The use of solid state junctions to convert ballistic charge carrier motion directly into electricity has recently been demonstrated in several novel methods and approaches. As shown in cross section in FIG. 1-A, in each case a charge carrier, most often an electron, is energized on or near a conducting surface 10A by an energizer 12A, such as chemical reactions with or without using conducting catalysts, using photovoltaic energizing materials, or using heat combined with a thermal gradient. In each case the charge carrier ballistically moves from a conductor 10A into a semiconductor or dielectric 11A. The conductor 10A is so thin that the electron effectively travels through it ballistically, without loosing energy or colliding with another electron or atom. The result is a voltage 14A across positive terminal 17A and negative terminal 16A. In FIG. 1-A, the dielectric junction 15A is a semiconductor junction specifically chosen to create an electrical potential voltage barrier which tends to impede the electron ballistic motion, shown as 11B in FIG. 1-B. FIG. 1-B shows the electrical potential in the device as a function of distance along the device. As shown in FIG. 2-A, electrons 21A at the conductor surface 22A have an energy greater than the top of the potential voltage barrier. These electrons 21A cross over the voltage barrier and lose energy to heat 24A before they settle down to the semiconductor conduction band 25A, which separates the charge across the conductor-dielectric junction. Electrons traveling against a potential voltage barrier convert some of the ballistic electron kinetic energy into electrical potential energy 27A. The rest of the ballistic electron kinetic energy becomes heat 24A. The voltage 27A developed is the difference between the Fermi level of the conductor on one side 28A and the Fermi level of the dielectric conductor electrode on the other side 26A. A voltage, V (Volts), is developed when the charges separate.
In a prior art, when energetic chemicals adsorbed on a thin conductor surface, electrons with energies greater than a voltage barrier of about 0.5 eV were detected in sensors similar to those represented by FIGS. 1-A, 1-B and 2-A. However, the energy distribution decreased exponentially beyond ˜0.1 eV, rendering the effect not useful for energy conversion and generation. Further, in those sensors the effective electron mass of the metal conductor 10A, of order 1 m_e, is much greater than the effective electron mass in the semiconductor 11A, typically silicon, of order ⅓ m_e. This results in most of the generated electrons being reflected away from the semiconductor/metal interface 15A, and therefore not collected. The relevance or utility of the role of electron effective mass has not been disclosed or expanded. The scheme also required the cryogenic cooling of the diode to reduce thermal noise. The efficiency of this scheme is so low that current can only be measured in the short circuit mode. The system can only be used as a chemical sensor and is not a useful electric generator.
In a prior system, association reactions on or near a conducting catalyst surface energized and initialized highly vibrational excited molecules. The energy of the vibrationally excited molecules was transferred to the electrons in the conductor. The electron energy was apparently in excess of a 1.2 volt barrier 11B. When a wide bandgap oxide semiconductor, TiO2 was used, useful short circuit currents at temperatures well exceeding the boiling point of water, (up to 473 Kelvin) are observed. Useful open circuit forward voltage was observed under conditions of almost zero temperature gradient at room temperature. The forward voltage was similar to that observed in a photovoltaicaly energized system using the same oxide semiconductor.
It would be highly advantageous to use a fabrication method resulting in predictable high output voltages and currents, and to be able to choose materials other than TiO2, to operate such a converter at an elevated temperature and to generate electricity in devices of this type using thermal gradients.
The field of solid state thermionics uses thermal gradients to energize charge carriers and uses semiconductor bandgap engineering to provide voltage barriers across semiconductor junctions. In such devices, charge carriers must travel ballistically through the dielectric 11A. No charge carrier ballistic travel is required in the material 10A. Moreover, it is acknowledged that charge carriers travel in all directions from material 10A towards the dielectric 11A. The effects of a step increase in the carrier effective mass during ballistic transport has not been used to enhance conversion efficiency and lower fabrication costs.
All known related converter concepts suffered an inefficiency directly related to the unspecified and therefore uncontrolled relative charge carrier effective masses of junction materials used. Nowhere does the field claim nor profess to claim any method or knowledge of tailoring or controlling carrier effective masses to enhance energy conversion efficiency.